The present invention relates to an anion conducting electrolyte membrane used in a solid polymer electrolyte type fuel cell, etc. and a manufacturing method thereof. In particular, the present invention relates to an anion conducting electrolyte membrane of low water uptake and high conductivity and a manufacturing method thereof, in which at least one part of grafts with halogenated alkyl groups has been converted into quaternary ammonium salt, which are introduced into a polymeric material comprised of a fluorine polymer for example.
Because the generating efficiency of the proton conducting fuel cell which uses hydrogen as a fuel is high, it may become a promising solution for the fossil fuel depletion. Moreover, because the carbon dioxide emissions can be greatly reduced in the proton conducting fuel cell, it also becomes the control means of global warming. Therefore, the development of the proton conducting fuel cell is hoped for domestic cogeneration and a power supply for cars. Especially, because a solid polymer type fuel cell uses the catalyst with high revitalization in addition to the low operation temperature and the low resistance of the electrolyte used, high power can be obtained even if it is small. Therefore, early implementation of the solid polymer type fuel cell is expected.
As for the anion conducting fuel cell which uses methanol or hydrazine as a fuel, the application to a fuel cell vehicle such as a compact car is especially advanced from simplicity of installing as the liquid fuel, high safety and high output density. Because the highly acidic condition is not needed in this proton conducting fuel cell when operating, cheaper iron or cobalt can be used as its electrodes, instead of precious metals such as platinum. Therefore, low-cost and high power fuel cell can be provided. However, it is a situation that the practical anion conducting electrolyte membrane is hardly developed. There is a major problem in that the conductivity, the mechanical strength, and the fuel permeability is remarkably low in a current anion conducting electrolyte membrane compared with time-proven Nafion® (a registered trademark of E.I. du Pont de Nemours & Co., Inc.) or the proton conducting electrolyte membrane.
In the anion type fuel cell, the anion conducting electrolyte membrane acts as so-called “electrolyte” to conduct the hydroxide ion (anion), and as “barrier membrane” to prevent methanol or hydrazine which is the fuel from mixing with oxygen. It is demanded as the polymer electrolyte membrane that the ionic conduction is large, chemical characteristics are stable so as to be tolerated in long-term use, the heat resistance is maintained for a long term at a temperature more than the operation temperature of the fuel, and the water holding property of the membrane is constant to keep ionic conduction high. On the other hand, it is demanded to have the excellent mechanical strength and dimensional stability of the membrane, and the high barrier characteristic to methanol, hydrazine, and oxygen from a viewpoint of the role as the barrier membrane.
The development of the anion conducting electrolyte membrane to solve said various problems has been actively advanced up to now. For example, the anion conducting electrolyte membrane, in which the anion exchange resin crosslinked is filled in the pores of a hydrocarbon film base material such as porous polyethylene is developed, and come on to the market (patent literatures 1-3). Moreover, a method of manufacturing the anion conducting electrolyte membrane, in which a basic material film made by polymerizing a mixture of haloalkyl styrene, elastomeric, and epoxy compounds is used, and the anion exchange groups are introduced by quaternization reaction is also presented (patent literature 4). Another method of manufacturing the anion conducting electrolyte membrane, in which the anion exchange groups are introduced after graft polymerizing the monomer which contains the groups on which the anion exchange groups can be introduced with the basic material comprised of fluorine polymer by radiation is also disclosed (patent literature 5).    Patent literature 1: JP 2002-367626 A1    Patent literature 2: JP 2009-203455 A1    Patent literature 3: JP 2010-092660 A1    Patent literature 4: JP 2011-202074 A1    Patent literature 5: JP 2000-331693 A1